Apache::DB establishes the needed hooks to debug mod_perl code interactively.
In order to use it,

- add the following code to httpd.conf, after loading mod_perl.so

<IfDefine PERLDB>

<Perl>
  use Apache::DB ();
  Apache::DB->init;
</Perl>

<Location />
  PerlFixupHandler Apache::DB
</Location>

</IfDefine>


- start apache for a debugging session using a line like:
httpd -X -DPERLDB -u


Then any perl request will be intercepted by the debugger.
Modules such as HTML::Mason have further hooks to get into the debugger
at interesting points.

This port also provides some sample configuration code that can
start up the debugger or the profiler in a similar way
(${PREFIX}/share/Apache/DB/perldb.conf)
